Men on paying sites tend to be a lot more serious about meeting a romantic partner and being in a serious relationship than men who use free dating sites.
Being that they have paid their hard-earned money to join a dating site, these men are going to be a lot more invested in finding someone.
These people may be trying out different online dating sites in order to find the right one for them.
It is always a good idea to diversify so as to increase the chances of the right one finding you or vice versa.
You never really know what online dating site is right for you until you have tried a few. This may be why you keep finding the same people across multiple online dating sites.